Embodiments of the disclosure relate to the field of semiconductor device fabrication. In particular, embodiments of the disclosure relate to a fin field effect transistor semiconductor device having a fingertip-shaped source or drain structure and method for manufacturing the same.
With the continuous development of fin field effect transistor (FinFET) devices, the parasitic external resistance has become a more dominant component at advanced technology nodes. The parasitic external resistance is due mainly to the contact resistance between the silicide and silicon in the source or drain region.
Most metals cause a strong Fermi level pinning effect, so that the position of the Fermi level is close to the middle of the silicon band gap, leading to a relatively high Schottky barrier height. As a result, the contact resistance increases. Due to the Fermi level pinning effect, it is difficult to reduce the Schottky barrier height. Equation (1) below shows the relationship between the contact resistance and the Schottky barrier height:
                              ρ          c                ∝                  exp          ⁡                      [                                                            2                  ⁢                                                                                    ɛ                        r                                            ⁢                                              m                        *                                                                                                              q                  ⁢                                                                          ⁢                  ℏ                                            ⁢                              (                                                      ϕ                    Bn                                                                              N                      D                                                                      )                                      ]                                              (        1        )            
where ρc is the contact resistance between the silicide and silicon in the source/drain region, ΦBn is the Schottky barrier height, ND is N-type dopant concentration, ∈r is the relative permittivity, m* is the electron effective mass,  is the Planck's constant, and q is the electron charge.
According to the prior art, the silicide layer in the source or drain region of the fin is the contact element. The following two cases may occur when forming the contact element:
1) silicide layers of adjacent source or drain regions may be joined together, so that the joined contact element has a relatively small area and the stress effect is reduced.
2) silicide layers of adjacent source or drain regions may not be joined together, but the volume of the epitaxial silicide layers is relatively small, the stress effect of the contact element may not be apparent, the surface of the contact element may have a polygonal shape, however, the surface area of the contact element is not sufficiently large, and the resistance of the contact element may be relatively large.
Thus, there is a need for methods for manufacturing a semiconductor device and a semiconductor device fabricated using such methods to solve the problems stated above.